The present invention relates to a power tool, particularly to a power tool for working by reciprocating a front tool such as a saw, a hammer, a chisel and scissors.
In a conventional power tool, the mechanism for converting the rotary motion of a motor rotator into the linear motion is adopted when cutting by the reciprocation operation. On the other hand, various types of linear motors are developed in the power tool with a linear motor. However, a lot of conventional linear motors have the structure which can be obtained by extending the rotating machine, and, as a result, obtain a straight line drive. For instance, the hammering device provided with a stator having a plurality of toroidal magnetic pole parts in a direction of the shaft line and an electromagnetic coil turned around a driving shaft is disclosed in the Japanese Patent Application Laid-Open No. 2000-79460.
In the mechanism for converting the rotary motion into the linear motion, it becomes a big trouble to cause a remarkable vibration and noise when working. On the other hand, the conventional linear motor has the structure which can be obtained by extending the rotating machine, and, as a result, obtains a straight line drive, as described above. Therefore, the motor efficiency is low because there is a lot of leakage flux between the movable element and the armature in the power tool with a linear motor. As a result, it is difficult to make practical in a power tool in which the high power is needed. In addition, the magnetic attraction power between the movable element and the armature works in one direction so that a big load may rest upon the support member of the movable element. As a result, the distortion is caused in the structure, various evils are caused, and it is, therefore, difficult to put into practical use.
An object of the present is to provide a power tool with a linear motor which can improve the motor efficiency and obtain the high power by reducing the leakage of the magnetic flux which passes between the armature and the movable element and reducing the magnetic attraction power produced between the armature and the movable element to cut out the mechanical section which is the source of the vibration and the noise in the power tool.
In a power tool with a linear motor according to one aspect the present invention, the linear motor comprises: a movable element installing a front tool at its one end and having magnetic poles installed at a fixed pitch along the direction of the movement; magnetic pole teeth installed in opposition to each other and at a fixed pitch along the direction of the movement in the vertical direction of movable element; and a coil for exciting the magnetic pole teeth so that the adjacent magnetic pole teeth and opposed magnetic pole teeth may becomes different poles, respectively. The linear motor further comprises a control circuit for reciprocating said movable element by exciting said coil to work something by using the front tool in the process of this reciprocating movement.
In a power tool with a linear motor according to another aspect the present invention, the linear motor has an armature formed with magnetic substance, a coil turned around the armature, and a movable element which can be relatively moved according to the action on the magnetic field produced by the armature. The linear motor has one row of the magnetic pole teeth connected magnetically to one magnetic poles of the armature and arranged with dividing into a first stage and a second stage in a direction substantially vertical to the direction where the movable element is moved, and the other row of the magnetic pole teeth connected magnetically to the other magnetic poles of the armature and arranged with dividing into a first stage and a second stage in a direction substantially vertical to the direction where the movable element is moved. The magnetic pole teeth of the first stage of the one row of the magnetic pole teeth and the magnetic pole teeth of the first stage of the other row of the magnetic pole teeth are alternately arranged in the direction where the movable element is moved, and the magnetic pole teeth of the second stage of the one row of the magnetic pole teeth and the magnetic pole teeth of the second stage of the other row of the magnetic pole teeth are alternately arranged in the direction where the movable element is moved. Further, the movable element is arranged between both rows of the magnetic pole teeth of the first stage and both rows of the magnetic pole teeth of the second stage.